In the context of non-supersymmetric SO(10) models, we analyze the renormalization group
equations for fermions from the GUT energy scale down to the electroweak energy scale, explicitly
taking into account the effects of an intermediate energy scale induced by a Pati–Salam
gauge group. To determine the renormalization group running, we use a numerical minimization
procedure based on a nested sampling algorithm that randomly generates the values of 19 model
parameters at the GUT scale, evolves them, and finally constructs the values of the physical observables
and compares them to the existing experimental data at the electroweak scale. We show
that the evolved fermion masses and mixings present sizable deviations from the values obtained
without including the effects of the intermediate scale.